The present invention relates to grates in general, and more particularly to improvements in rotary grates for transport of fuel, clinker, slag or the like. Still more particularly, the invention relates to improvements in grates which are designed to supply combustion air in a furnace (e.g., in a large industrial furnace) to promote the oxidation of fuel, clinker or the like.
German Pat. No. 612,972 discloses a rotary grate which is formed with openings for admission of combustion air into a layer of clinker which rests on and is conveyed by the grate. The rotary grate is installed at the discharge end of an industrial furnace to transfer clinker into an evacuating duct. The rotary grate is disposed above a chamber which receives air by way of a pipe and the upper end of which is substantially sealed by the grate. The grate has slots or holes for reception of air from the chamber while the slots or holes travel above the upper end of the chamber, and such air passes through the interior of the rotary grate and contacts the layer of clinker by passing through those slots or holes which are out of register with the upper end of the chamber. The layer of clinker is thereby completely combusted prior to entering the aforementioned evacuating duct. Air which enters the rotary grate by way of the slots or holes also serves to cool the grate. However, the cooling action of air which is supplied by the chamber is not uniform and not predictable with a requisite degree of reproducibility. As a rule, the cooling action varies at random, as considered in the axial direction of the rotary grate. For example, if the layer of clinker heats the rotary grate to a temperature at which the adjacent particles or batches of clinker begin to flow, the thus obtained liquefied clinker adheres to the periphery of the grate and is likely to clog the air-discharging slots or holes. Consequently, air streams issuing from the chamber cannot leave the grate in those regions which require a most pronounced cooling action. This leads to accumulations of additional liquefied clinker which thereupon sets or hardens and forms a crust which prevents the outflow of any air. Air issuing from the chamber then begins to flow around the grate and past the customary sealing strips so that the quantity of air entering the interior of the grate decreases still further. The temperature of the grate continues to rise so that the thickness of the crust of liquefied and subsequently hardened clinker increases to form an envelope which can interfere with or even prevent rotation of the grate.